Enhanced corrosion resistance in accident-tolerant FeCrAl alloy by water-assisted laser surface modification

Y. Hua, Y. Linga, F. Zhaoa, H. Zhonga, T. Xua, Y. Baib and Z. Zhanga

Journal of Materials Processing Technology 306, 117640 (2022)
FeCrAl alloys have been widely developed as an alternative accident-tolerant cladding material in light water reactors since the Fukushima nuclear accident in 2011. A large thermal neutron cross-section is the most severe challenge for FeCrAl alloys in the final commercial use, and a thinner cladding was necessary to overcome this, which led to higher corrosion resistance requirements. To address this issue, a surface treatment process is described here to enhance the corrosion resistance of the FeCrAl alloy via a water-assisted laser modification. By varying the laser power and laser scanning speed, the relationship between corrosion and processing parameters was investigated to better understand the mechanism with various characterizations. A heat-transfer model with boiling heat transfer boundary conditions was built and simulated using a finite element method to reveal the change in temperature field during processing. A corrosion test was performed with a simulated light water reactor (LWR) hydro-thermal environment for 120 h. The corrosion rate and oxide film thickness of the water-assisted laser modified FeCrAl alloy sample decreased by 83 % and 50 %, respectively, compared to the as-received one, and this was ascribed to the formation of protective oxide film during laser processing, along with grain refinement and elimination of holes and scratches.